1. Field of the Invention
The present invention relates to a display panel contact apparatus, more particularly relates to a display panel contact apparatus capable of bringing contactors formed on a pliable film into contact with signal line terminals of a color liquid crystal display panel with a required pushing force so as to cause the color liquid crystal display panel to light up and display a selected color. Further, the present invention relates to a flexible printed circuit board in which it is possible to efficiently perform inspection of conduction after connecting a plurality of conductive patterns to a connector, IC tab, or other electronic component with a plurality of electrode patterns arranged at close distances or a large number of terminals formed in a row, an electrical connecting apparatus utilizing this, and a method of using the same.
2. Description of the Related Art
In general, a liquid crystal display panel of the active matrix system is formed by arranging a pixel at each intersecting portion of signal lines laid in the form of a lattice. Each pixel is comprised of a switching element made of a thin film transistor, a transparent pixel electrode connected to one electrode (drain electrode) thereof, and a transparent common electrode arranged facing this transparent electrode via a liquid crystal. Further, in the color liquid crystal display panel, a color filter comprised of dots of three colors of red (R), green (G), and blue (B) arranged in the form of a matrix is used. At the same time, the above transparent pixel electrodes are arranged corresponding to the dots of these colors. Further, in this type of liquid crystal display panel, terminals of the pixel electrode signal lines connected to the electrodes of the above pixel switching elements (source electrodes and gate electrodes), terminals of the common electrode signal lines connected to the transparent common electrodes, etc. are formed on a transparent insulating substrate at the periphery of the liquid crystal display portion arranged divided into blocks for every driving module. Conventionally, in order to inspect the display quality etc. of this type of liquid crystal display panel before connecting and fixing peripheral circuits such as the driving module, generally use has been made of a liquid crystal display panel inspecting apparatus which brings contactors formed by a conductor on one surface of a film substrate, generally referred to as a "contact film", into contact with the above signal line terminals of the liquid crystal display panel with a required pushing force so as to light up the liquid crystal display panel (for example, refer to Japanese Unexamined Patent Publication (Kokai) No. 2-78969).
In such a conventional color liquid crystal display panel inspecting apparatus, generally a single liquid crystal driving signal is simultaneously supplied to the signal line terminals for the separate-color pixel electrode of the color liquid crystal display panel via the contactors formed on the film substrate so as to light up the three colors of pixels to make the color liquid crystal display panel light up with a white color. Accordingly, generally the contactors on the film substrate in the conventional color liquid crystal display panel inspecting apparatus are formed into patterns in a direction cutting across the signal line terminals for the separate-color pixel electrodes so as to simultaneously contact the signal line terminals for the separate-color pixel electrodes of the color liquid crystal display panel. Accordingly, the signal supply wiring pattern connected to the contactors for contact with the signal line terminals for the pixel electrodes may be a streamlined, simple pattern and may be easily formed on one surface of the film substrate together with the wiring pattern connected to the contactors for contact with the common electrode signal line terminals.
In recent years, demand has been growing for strictly performing the lighting inspection of the color liquid crystal display panel by separate color. In this case, it is necessary to form the contactors on the film substrate at the same pitch as the signal line terminals for the separate-color pixel electrodes in the color liquid crystal display panel and, at the same time, it is necessary to individually supply signals to three contactor groups corresponding to the groups of the signal line terminals for the separate-color pixel electrodes. Therefore, where it is desired to form the signal wiring for individually supplying signals to these three contactor groups as independent patterns for each type of contactors on one surface of the film substrate together with the contactors, a pitch much larger than the pitch of the contactors must be secured at the signal input end of the signal wiring. Therefore the width of the film substrate is increased and the flexible printed circuit board, connector, etc. for connection with the signal wires on the film substrate become large and therefore it becomes impossible to form a portable contact-socket type display panel inspecting apparatus.
On the other hand, the problem can be solved if the signal wiring connected to each group of contactors on the film substrate has a pattern and shape terminated at the signal input end, but since the separate color pixels are formed alternately three colors at a time, it is impossible to form the signal wiring to be respectively connected to the three contactor groups corresponding to the separate color pixel electrode signal line terminal groups on one surface of the film substrate without causing short circuiting. Further, the method may be considered of dividing a single signal wire at the position of the branched wiring in the vicinity of the contactors, forming the portion of the wiring of the signal input end on the reverse surface of the film substrate, connecting the portion of the wiring of the signal input end and the portion of the wiring of the contactor side by through holes, and thereby forming a three-dimensional circuit, but a very large number of through holes of the same number as that of the contactors becomes necessary. Further, the branched wiring parts in the vicinity of the contactors have a very fine pitch, therefore a high level of precision is required for the formation of the through holes and, at the same time, a high positioning precision is required for the formation of the two portions of the wiring on the two surfaces of the film substrate. This causes a great rise in the manufacturing costs.
Further, in general, a plurality of IC tabs each configured by mounting a drive IC chip on an insulating film are respectively connected to the source side electrodes and the gate side electrodes on the substrate of the liquid crystal display panel. Accordingly, the individual source side electrodes and individual gate side electrodes of the liquid crystal display panel are formed together with common electrodes into blocks for each number of electrodes corresponding to the number of output side electrodes of the IC tabs.
In the process of manufacturing such a liquid crystal display panel, the inspection of the display quality etc. for detecting defective portions of the display is carried out for the liquid crystal display panel before connection of peripheral circuits such as the above IC tabs. Accordingly, in this type of inspection, a contact apparatus provided with contact members for contact with the electrodes arranged on the substrate of the liquid crystal display panel before the connection of peripheral circuits has been used. For example, as shown in Japanese Unexamined Patent Publication (Kokai) No. 6-08034, as the contact members for contact with the electrodes of the liquid crystal display panel, conventionally needle-shaped or wire-shaped probes and contact films constituted by forming contact conductor patterns on base films having pliability and an insulating property have been known. Along with the higher density and finer pitch of the electrodes, contact films have tended to be adopted from the viewpoints of the reliability of contact with the electrodes, facility of handling, and manufacturing costs.
In the liquid crystal display panel inspecting contact apparatus used in such an inspection, generally a contact film 8 as shown in FIG. 36 and FIG. 37 is used. The contact film 8 shown in the figures is comprised of a flexible substrate 8a having an insulating property and an IC tab 5 connected to one end of the flexible substrate by an anisotropic conductive sheet, soldering, or the like. A plurality of conductive patterns 8b arranged in parallel at a fine pitch are formed on one side surface of the flexible substrate 8a. The connection terminals of the IC tab 5 are individually connected to these conductive patterns 8b.
The contact film 8 configured as described above is brought into contact with one of the individual electrode groups 9a comprised of a predetermined number of electrodes of a liquid crystal display panel 9. The conductive patterns 8b are individually connected with the individual electrodes. Accordingly, by using the above contact film 8, individual electrodes extending from the liquid crystal display panel 9 can be reliably inspected one by one.
The conductive patterns 8b of the contact film 8 are formed precisely corresponding to the high density arrangement of the individual electrodes with a precision of for example about 0.01 mm. An extremely sophisticated level of technology is required for connecting the IC tab 5 to the conductive patterns 8b. For this reason, an extremely high precision becomes necessary for connecting the flexible printed circuit board 8a and the IC tab 5, so the inspection of conduction after connection could not be eliminated. However, it is extremely difficult to individually inspect a plurality of fine conductive patterns 8b formed on a completed contact film 8 and it is necessary to raise the inspection efficiency.